KITCHENER -- An Ontario city is investigating after hundreds of thumbtacks and sewing needles were found on one of its public playgrounds.

Staff for the City of Woodstock say they were found Wednesday morning while a mother and her daughter were playing at Southside Park.

Now they're warning the public about the discovery.

“They were on top of the playground equipment and on the slides and swings, as well as at the base of slides and stairs going onto the playground equipment where children are using the equipment,” says Reta Horan, the Supervisor of Parks and Forestry for the city.

Officials call it a “disturbing” discovery, but say this isn’t the first time that sharp objects have been found at that location.

"This is the second act of vandalism in Southside Park with intent to injure," a Facebook post from the city reads in part. "Earlier this month, Woodstock Police were also called to investigate the spread of nails throughout the cricket pitch and nearby playing area."

The city immediately closed the park, so they could inspect and clean up the needles and tacks.

“We had a few different magnets that you use to pick up roofing nails or any metal objects,” says Horan. “We went over the playground quite a few times.”

Southside Park has reopened, but some say they’re concerned by these incidents.

“I can’t imagine why somebody would do something like that,” says one park-goer.

Meghan Clifford went to the park with her kids on Wednesday.

“One of the city workers were pulling up in their truck and I asked them what was going on,” she says. “They said they were cleaning it up because they found sewing needles and thumbtacks.”

Clifford is disappointed that someone would do something like this.

“It’s crazy,” she says. “How anyone would want to do that to kids, especially in a park.”

Officials are reminding the public to be diligent after these two incidents.

“It makes us apprehensive,” says Horan. “We’re doing more checks of our parks. We’re making sure that we’re checking them as often as we can. That's why we wanted to let the public know, so that everybody could take a look before their kids start playing and be aware of the situation so that we can make sure everyone is safe and still able to use our parks."

Police are now investigating these incidents and are asking anyone who has witnessed anything suspicious to give them a call.